1. Field of the Invention
This present invention relates to a digital image stabilization apparatus for compensating a jitter occurred in one of the frames among a video sequence.
2. Description of the Prior Art
The current design for digital cameras and video camcorders gravitates towards light-weight and compact. When these light-weight and compact digital cameras or video camcorders are used, undesired shake or jitter, caused by environment or users, on these digital cameras and video camcorders are inevitable. Therefore, the undesired shake or jitter, subjected to the digital cameras or video camcorders, will result in blurred images or an abrupt change occurred in a frame among a video sequence. It is annoying for users to watch the jerky images or videos resulting from undesired shake or jitter. Therefore, it is an important topic to avoid shake or jitter on cameras or camcorders, or to adjust the blurred images so as to improve the image quality.
There is an approach been developed to adjust the blurred images captured by digital cameras and video camcorders. The prior art is, firstly, to divide all frames among a captured video sequence into a plurality of blocks. Next, the prior art is to compare all of the blocks of one of the frames with all of the blocks of the frame previous to the compared frame to respectively find out the blocks on such two frames that exhibit the same image, but locate different positions. The prior art is then to compute the relative distances (or so-called motion vectors) between the found-out blocks on such two frames. The computed relative distances (or motion vectors) are then used to adjust the last one of such two frames, and thereby remove the undesired shake or jitter occurred in the last one of such two frames.
However, there are two major problems existing in the aforementioned approach while considering hardware implementation. Firstly, since a digital image stabilizer disclosed in the prior art needs an extra buffer for storing all of the blocks of the previous frame before the comparison process is performed, the prior art increases the requirement of memory. Secondly, the comparison process of the prior art takes an exhaustive search strategy for the found-out blocks between such two frames to estimate the relative distances (motion vectors), which involves intensive computational operation and high power consumption. Unfortunately, the power management is also a critical issue on the design of digital cameras, video camcorders or other hand-held electronic apparatuses.
There is also another prior art relating to the image stabilization by use of an optical device, such as a gyro-sensor. The aforesaid prior art uses a gyro-sensor to detect shake (or jitter) subjected to a camera (or a video camcorder), and then shift a correction lens inside the lens system to eliminate the detected shake (or jitter). Obviously, the aforesaid prior art increases the overall cost due to additional gyro-sensor and more complicated design of lens system. Besides, the aforesaid prior art can not be applied in light-weight and compact electronic devices due to extra controlling circuit.
Accordingly, a major objective of the invention is to provide a digital image stabilization apparatus to overcome the aforementioned problems.